Moisturized and oxygen enriched air is frequently used for inhalation therapy in a variety of different patient conditions. Different types of instruments, nebulizers for providing water particles, and humidifiers for providing water vapor, are used for different inhalation therapies. Some of these therapies require use of a nebulizer to provide moisturized oxygen enriched air in which the moisture is in the form of particles. The nebulizer provides moisture that is forced deep into the patient's lungs. However, a humidifier rather than a nebulizer is employed where it is desired to moisten tissues within the breathing passages of the patient, and where injection of water particles more deeply into the patient's breathing passages and lungs is not desired.
Nebulizers of various types can provide a wide range of total flow rates of moisturized breathing mixture to the patient from very small amounts, in the order of 10 liters per minute or less, to high amounts, as high as 100 liters per minute or more. However, most bubble type devices, a simple type in which a stream of air or oxygen enriched air is caused to flow or bubble through a liquid to entrain water vapor, are capable of total output flow rates of no more than about 10 to 12 liters per minute. If a higher flow rate of humidified breathing gas mixture is required, exceedingly complex and very costly ventilating equipment must be employed to provide the desired high flow rate of vapor entraining air mixtures. These systems use complex arrangements of flow generators, ventilators and heated humidifying equipment. Such arrangements may cost in the order of many tens of thousands of dollars, as compared to disposable nebulizers or humidifiers which may be available for as little as $10.00 or less. Inexpensive disposable humidifiers of high flow rates are not available.
In a treatment known as Constant Positive Airway Pressure (CPAP), a continuous positive pressure of moisturized breathing mixture is provided to the patient. Such treatment at present is performed with the exceedingly expensive ventilating equipment, which is effective over long periods. Alternatively, such treatment can be performed. with a disposable gas injection nebulizer, such as shown in U.S. Pat. No. 4,767,576 for Nebulizer with Auxiliary Gas Input, assigned to the assignee of the present application. Such a nebulizer is effective for use in the CPAP treatment for relatively short periods of time, but must be turned off periodically in order to avoid excessive water build-up in the patient's breathing mask.
Accordingly, it is an object of the present invention to provide a moistened breathing mixture that contains water vapor but minimal water particles and which can provide a very high flow rate of the vapor entraining breathing mixture at relatively low cost.